With Argentina now in possession of a conditional offer to join the Tri-Nations, the landscape of world rugby is set to change.

The Pumas will join the southern hemisphere's premier competition in 2012 should they fulfil the criteria laid down by SANZAR, ending a long process that began in the wake of their third place finish at Rugby World Cup 2007 in France.

With this in mind, we take a look back at some of the most significant changes in the game in our latest Scrum Seven.

And then there were six - Italy added to the Five Nations - 2000

The 1990s represented a low-point for Celtic rugby, with England and France dominating the much-loved Five Nations Championship to such an extent that their continued participation was questioned.

The answer to this conundrum came in the shape of Italy's admission to the championship and the launch of the Six Nations in 2000. The Italians' first game was a 34-20 triumph over reigning champions Scotland at the Stadio Flaminio in Rome. While they have won only five games since, all against Scotland or Wales, the Six Nations has become a far more competitive tournament since their introduction.

Since 2000 France have won four tournaments, with two Grand Slams, England have won three with one Grand Slam, Wales have won two Grand Slams and Ireland last season ended a 61-year wait with a Grand Slam to add to their Triple Crowns in 2004, 2006 and 2007.

Super, thanks for asking - SANZAR wades in - 1995

Following the success of the 1995 Rugby World Cup in South Africa and the sea-change move to professionalism, the newly formed SANZAR alliance stepped in to shake up domestic and international rugby in the southern hemisphere.

The result was the formation of the Super 12, replacing the amateur era's Super 6 and Super 10, and the Tri-Nations, a Test series between the best the world game had to offer in Australia, New Zealand and South Africa.

Tri-Nations

Seen by some as an unofficial world championship every year, the Tri-Nations formalised some of the greatest rivalries in world rugby.

The Bledisloe Cup, contested by Australia and New Zealand, and the roaring clashes between the All Blacks and Springboks would have even more on the line. Generating 60% of SANZAR's revenue through TV deals, it's easy to see the magnitude of Argentina's admission.

New Zealand have dominated the landscape since 1996, winning all but five championships. Only two great sides, the John Eales-led Wallabies in 2000 and 2001 and the 2009 Springboks have placed serious doubts on their stranglehold.

Super 12

A franchise structure similar to that operated in American sports formed the basis for the southern hemisphere's new domestic competition, regional hubs usurping domestic sides from the NPC in New Zealand, Currie Cup in South Africa and Australian city competitions.

With 12 franchises originally contesting the competition (five from New Zealand, four from South Africa and three from Australia) the tournament has been dominated by New Zealand's Canterbury-based Crusaders, who have won seven titles.

Its popularity has led to expansion, driven also in part by Australia's lack of a domestic competition, with 14 teams contesting the tournament from 2006 and 15 from 2010.

What's in a name? Wales goes regional - 2003

The regionalisation of Welsh club competition brought the curtain down on some of the most famous names in world rugby, with Pontypridd, Pontypool, Bridgend and eventually Llanelli, Neath and Swansea disappearing from the elite stage.

In the place of the famous Welsh club structure came the centralised, more financially viable, regions in 2003. Under the guidance of WRU chief David Moffett the sentimental vote was ignored, with Cardiff Blues, Celtic Warriors, Dragons, Ospreys and Scarlets consuming the club structure at full professional level, leaving the semi-professional Principality Premiership in their wake.

Since regionalisation at domestic level, Wales have won two Grand Slams while the Ospreys have won a brace of Magners League titles. On the flipside, the Bridgend-based Warriors were disbanded in 2004 due to financial struggles, bequeathing one of Welsh rugby's true heartlands to rugby league and the Celtic Crusaders Super League franchise.

We are the champions - The Heineken Cup changes European rugby - 1996

With Test match levels of intensity and sold-out signs adorning grounds across Europe, the Heineken Cup has grown to become one of the great products of the professional game.

Mimicking the famous European Cup in soccer, the tournament's first final in 1996 pitted now three-times winners Toulouse against Cardiff at the old National Stadium.

For the first time the top clubs from across Europe could be measured against one another, with French clubs immediately embracing the tournament and exerting a stranglehold on proceedings until Jon Callard inspired Bath to victory in 1998.

Since then Irish province Munster has developed an almost mythical affinity with the tournament, their eventual triumph at the third time of asking in 2006 elevating the final to new levels of drama.

It's about time - England gets a league structure - 1987

With the London Double Header and Saracens' day out at Wembley having pulled in over 100, 000 fans in the past two weeks, it is easy to forget the Premiership's humble beginnings.

In 1972, the RFU sanctioned a nationwide Cup competition but it was not until 1987 when their resistance to a formal league was broken and the Courage Leagues were formed. Clubs organised their own fixtures in a piecemeal fashion until 1994, with Bath and Leicester enjoying great success.

Wasps won the first professional league in 1997, but the new, wealthy competition also had its casualties with famous names Richmond and London Scottish disappearing under a cloud of financial problems.

In 2000 the modern Premiership took over, struggling at first to cement an identity through format changes but hitting its stride with the now popular playoff structure in 2003, when Wasps again prevailed.

Au revoir - France expelled from the Five Nations - 1931

France officially joined the International Championship in 1910, bringing the Five Nations in to existence on an official basis.

After 21 fruitless years the French were banished from the tournament in 1931 however, following allegations of professionalism and claims that players had on occasion hidden stiletto knives in their socks.

The championship had been marred by infighting before; it was not completed in 1885, 1887 and 1889, but this step brought about the retroactive Home Nations championship until the tournament was placed on hold during World War II.